Starting a store with WordPress is pretty easy these days. Dealing with fake customers as your store starts growing takes some effort though. Fake Customer Blocker for WordPress is a handy plugin that lets you block emails from banned domains to be used for new orders.
This plugin stops certain visitors from submitting orders based on their email, ID, zipcode, or country. It can be used to block users on the registration page or at checkout. You can display custom messages to blocked customers.